This invention relates to a scroll compressor wherein a motor protector is placed in a location such that suction refrigerant cools the protector. Thus, upon a reduction in the refrigerant mass flow the protector will become heated, and trip.
Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor a pair of scroll members each have a base and a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. One of the two scroll members is caused to orbit relative to the other. As the wraps orbit relative to each other, the size of the compression chambers decreases and an entrapped refrigerant is compressed.
There are many challenges with scroll compressor design. One of the challenges relates to the mass flow through the compressor. The compressors are typically incorporated into a refrigerant cycle, and there is the possibility of loss of charge in the refrigerant from any spot in the cycle. During a loss of charge situation, the mass of refrigerant flowing through the compressor decreases. Continued operation at loss of charge situations can have undesirable side effects. Thus, there is an effort to identify loss of charge situations.
One protection element incorporated into compressors is a motor protector. A motor protector senses several variables within the compressor housing, and stops operation of the electric motor driving the compressor should conditions indicate some problem with the compressor or its associated refrigerant cycle. Typically, the protector is actuated by an anomaly in the power supply to the electric motor (i.e., a spike in voltage or current) or, due to excessive heat. Motor protectors have been typically incorporated into the windings of the motor stator. Thus, the motor protector has typically been removed from the compressor pump elements, and away from any location likely to be effected by the refrigerant flow.
In a disclosed embodiment of this invention, a motor protector is positioned in a sealed compressor at a location such that it will be exposed to the flow of suction refrigerant. The motor protector is thus cooled by the suction refrigerant, and the suction refrigerant thus reduces the likelihood of the protector tripping. As known, the motor protectors have circuitry that enable them to trip if there is an electrical anomaly, or if there is an increase in temperature beyond a predetermined amount. The predetermined amount can be designed into the protector. With the present invention, the predetermined amount is designed such that it anticipates the flow of suction refrigerant over the protector to cool the protector. Thus, the predetermined amount might be somewhat lower than would typically be the case with a motor protector.
Should there be a reduction in the mass flow of refrigerant, the protector will no longer be cooled by the suction refrigerant to the same extent. The motor protector is then more likely to exceed a trigger temperature and trip, stopping operation of the motor. In embodiments of this invention, the protector is positioned either axially spaced away from the windings, or radially outward of the windings. Preferably, the protector is positioned in the path of the suction refrigerant. This can be achieved in any of several ways.
In one general category of embodiments, the protector is positioned spaced adjacent the suction tube. In this way, the suction fluid is directed onto the protector. Various structures may be associated with the protector such as a baffle, or a shield of some type. These structures increased the sensitivity of the protector to the mass flow of suction refrigerant. Alternatively, a heat pipe can conduct heat away from the protector to a location at which the heat pipe is cooled by the suction refrigerant. Again, should the mass flow of suction refrigerant decrease, the heat transfer from the protector will decrease and the protector is then likely to trip.
In other embodiments of this invention, the protector may be surrounded by the start windings of the motor. In this way, the protector is heated, and if not cooled by the suction refrigerant, it will trip.
Various other ways of transferring heat from the protector through the refrigerant flow are disclosed.
These and other features of this invention can be best understood from the following specification and drawings, the following of which is a brief description.